Re: [PATCH i-g-t v9 29/49] lib/unigraf: Add helpers to read and write edid

[Louis Chauvet <louis.chauvet@bootlin.com>]

On 3/23/26 17:26, Kamil Konieczny wrote:
> Hi Louis,
> On 2026-03-16 at 17:17:50 +0100, Louis Chauvet wrote:
>> Read and writing EDID on unigraf can be useful to emulate different
>> screens, add helpers to read and write them.
>>
>> There is a limitation on the libTSI.so, it is only possible to read EDID
>> using buffers of size multiple of 128 bytes, and there is no way to query
>> the actual EDID size. The current implementation can only read EDID up to
>> 2048 bytes.
>>
>> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
>> Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
>> ---
>>   lib/unigraf/unigraf.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>   lib/unigraf/unigraf.h |  4 ++++
> 
> Please move all unigraf libs into lib/vendors/unigraf/
> similar to uwildmat use case.

Ack, I will do it for the next iteration.

>>   2 files changed, 63 insertions(+)
>>
>> diff --git a/lib/unigraf/unigraf.c b/lib/unigraf/unigraf.c
>> index b752ff573ace..d06da6742e95 100644
>> --- a/lib/unigraf/unigraf.c
>> +++ b/lib/unigraf/unigraf.c
>> @@ -56,6 +56,11 @@ static char *unigraf_connector_name;
>>    */
>>   #define UNIGRAF_DEFAULT_INPUT_NAME "DP RX"
>>   
>> +/**
>> + * EDID_MAX_SIZE - Max EDID size that can be read from the unigraf. The
>> + */
>> +#define EDID_MAX_SIZE 2048
>> +
> 
> Is this unigraf specific? For local def maybe UNIGRAF_EDID_MAX_SIZE?

This is a limitation of my unigraf hardware. My current implementation was:
	
	size = TSIX_TS_GetConfigItem(dev,EDID_TE_INPUT,0,0);
	buf = malloc(size)
	TSIX_TS_GetConfigItem(dev,EDID_TE_INPUT,buf,size);

but TSIX_TS_GetConfigItem don't give the real size but min(buf_size, 
real_edid_size) (and sometimes worse: if size is not % 128, it can do 
buffer overflow...)

That why I always allocate a "big" buffer to ensure the %128 and to get 
the real_size.

I will rename the constant, thanks!

> Regards,
> Kamil
> 
>>   static void unigraf_close_device(void)
>>   {
>>   	if (!unigraf_device)
>> @@ -127,6 +132,20 @@ static void unigraf_init(void)
>>   		value;												\
>>   	})
>>   
>> +/**
>> + * unigraf_write() - Helper to write a value to unigraf
>> + * @config: config id to write
>> + * @data: data to write
>> + * @data_len: length of the data
>> + * Returns
>> + */
>> +static void unigraf_write(TSI_CONFIG_ID config, const void *data, size_t data_len)
>> +{
>> +	unigraf_debug("Writing %zu bytes to 0x%x\n", data_len, config);
>> +
>> +	unigraf_assert(TSIX_TS_SetConfigItem(unigraf_device, config, data, data_len));
>> +}
>> +
>>   /**
>>    * unigraf_device_count() - Return the number of scanned devices
>>    *
>> @@ -329,6 +348,46 @@ void unigraf_reset(void)
>>   	unigraf_set_sst();
>>   }
>>   
>> +/**
>> + * unigraf_read_edid() - Read the EDID from the specified stream
>> + * @stream: The stream ID to read the EDID from
>> + * @edid_size: Pointer to an integer where the size of the EDID will be stored
>> + *
>> + * Returns: A pointer to the EDID structure, or NULL if the operation failed. The caller
>> + * is responsible to free this pointer.
>> + */
>> +struct edid *unigraf_read_edid(uint32_t stream, uint32_t *edid_size)
>> +{
>> +	void *edid;
>> +
>> +	unigraf_debug("Read EDID for stream %d...\n", stream);
>> +
>> +	edid = calloc(EDID_MAX_SIZE, sizeof(char));
>> +
>> +	unigraf_write_u32(TSI_EDID_SELECT_STREAM, stream);
>> +	*edid_size = unigraf_assert(TSIX_TS_GetConfigItem(unigraf_device,
>> +							  TSI_EDID_TE_INPUT,
>> +							  edid, EDID_MAX_SIZE));
>> +
>> +	return edid;
>> +}
>> +
>> +/**
>> + * unigraf_write_edid() - Write EDID data to the specified stream
>> + * @stream: The stream ID to write the EDID to
>> + * @edid: Pointer to the EDID structure to write
>> + * @edid_size: Size of the EDID data in bytes
>> + *
>> + * This function writes the provided EDID data to the specified stream.
>> + */
>> +void unigraf_write_edid(uint32_t stream, const struct edid *edid, uint32_t edid_size)
>> +{
>> +	unigraf_debug("Write EDID for stream %d...\n", stream);
>> +
>> +	unigraf_write_u32(TSI_EDID_SELECT_STREAM, stream);
>> +	unigraf_write(TSI_EDID_TE_INPUT, edid, 2048);
>> +}
>> +
>>   /**
>>    * unigraf_hpd_assert() - Assert Hot Plug Detect signal
>>    *
>> diff --git a/lib/unigraf/unigraf.h b/lib/unigraf/unigraf.h
>> index c2caa9c2c54c..40f706ebd483 100644
>> --- a/lib/unigraf/unigraf.h
>> +++ b/lib/unigraf/unigraf.h
>> @@ -42,6 +42,10 @@ void unigraf_require_device(int drm_fd);
>>   
>>   void unigraf_reset(void);
>>   
>> +struct edid *unigraf_read_edid(uint32_t stream, uint32_t *edid_size);
>> +
>> +void unigraf_write_edid(uint32_t stream, const struct edid *edid, uint32_t edid_size);
>> +
>>   void unigraf_hpd_deassert(void);
>>   
>>   void unigraf_hpd_pulse(int duration);
>>
>> -- 
>> 2.52.0
>>